Refrigerating apparatus



Oct. 27, 1931. R. K. MILLER 11,829,417

REFRIGERATiNG APPARATUS Filed NOV. 30. 1927 STATES rant RALPH K. mm, OFDAYTON, OHIO, ASBIGNOB, BY MESNE ASSIGNMENTS, T FRIGID- AIBE COBPOBATION, A. CORPORATION OF DELAWARE BEBRIGEBATING AEPABATUSApplication filed November 30, 1927. Serial No. 286,717.

This invention relates to refrigerating apparatus and particularly to anovel method of lubricating such apparatus.

One of the objects of the invention is to provide positive and regularcirculation of lubricant in refrigerating apparatus. More specificallyit is an object of the invention to return lubricant from theevaporating or expander to the compressor of a refrigerating [0 system.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings,- wherein a preferred [5 form of the present invention isclearly shown. In the drawings;

Fig. 1 is a conventional or diagrammatic representation of arefrigerating system in go which my invention is embodied, and

Fig. 2 is a vertical longitudinal section thru a portion of theevaporator of such system.

Fig. 1 shows a compressor-condenser-expander type of refrigeratingapparatus hav- 5 ing an evaporator and a condensing element including acompressor 11, a condenser 12, and a receiver, or liquid refrigeranttank 13. Refrigerant vapor is withdrawn from the evaporator thru thevapor or low pressure conduit 14 and is liquefied in the condenser 12and returned to the evaporator thru the liquid or high pressure conduit15. The compressor is operated by a motor 17 controlled by an automaticswitch 18 which may be actuated in response to the refrigerating demand,for example by a pressure responsive device 19 connected to the lowpressure conduit 14.

Referring to F 2, the evaporator comprises a header 20 forming areservoir for liquid refrigerant, and a number of tubes or ducts 21 deending from the header for circulating re rigerant. The liquidrefrigerant is indicated by 22 and is kept at a constant level 23 by avalve 24 actuated by afloat 25. The liquid refrigerant is supplied by aconnection 15 and the vapor is withdrawn thru a tube 14: connected tothe vapor con duit 14.

All of the apparatus above described is Well known in the art and itsparticular form and arrangement is immaterial to the present invention.It has been customary to lubricate the compressor of suchsystems byplacing a quantity of oil in the crank case and depending upon thesplashing ofthe rotating parts to distribute the oil thruout thecompressor. Some of the oil is dissolved in the refrigerant, and some ofthe oil is mechanically pumped by the compressor to the condenser andreceiver and eventually to the evaporator. The refrigerant boils off inthe evaporator, leaving the oil, which collects in a layer from inch to'1% inches thick on top of the refrigerant.

A great deal of trouble has been experi;

enced in the past because this oil could not be effectively removed fromthe evaporator, Not only does the collection of oil in the evaporatorexhaust the supply of lubricant in the compressor, but it also hindersevaporation of the refrigerant, causing the pressure and consequentlythe temperature of the refrigerant to increase. Various arrangementshave been attempted for periodically or regularly extracting this oilfrom the evaporator and returning it to the compressor. One of thoseproposed and widely in use is the evaporator exhaust connection 14.shown in Fig. 2. This is a tube projecting into the evaporator andhaving its open end 25 above the level of the oil layer. One or moredrain openings 26 are formed in the side of the tube below the level ofthe opening 25 and also below the estimated level of the oil but abovethe estimated level of the liquid refrigerant. The theory of thisarrangement is that the refrigerant vapor will be withdrawn from the topof the header thru the opening 25 by the suction of the compressor andthat whenever the oil level used for refrigerating apparatus lie on topreaches the opening 26, oil will drain out of drawn without removingthis definite quan the evaporator. However, this arrangement tity ofoil, consequently a positive and re'guhas proved unsatisfactory andunreliable in lar circulation of oil is effected.

service, and as far as I am aware, no plan I have also discovered thatwhile the oil for removing oil has been completely sucpreviously usedwill form a very thick layer cessful. It is well known that evaporatorson top of the refrigerant, sometimes as much of this character maycollect oil until the as 1% inches, these foaming oils do not formcompressor is completely dry, and that while such a thick layer. Themaximum thickness oil may be returned to the compressor at inof thefoaming oil layer which I have obtervals, the return-is extremelyIrregular and served is about A, inch. This characetristic the apparatuswill frequently operateas'much materially improves the operation of theas sixty days without returning any oil whatevaporator, because theboiling temperature ever to the compressor. of the refrigerant is notincreased materially .I-havediscovered that the oils heretofore by thisthin layer of oil. 7

, The oils which I have found particularly of the refrigerant in a thicklayer which is suitable are certain paraffin base oils" from quite solidand is free from bubbles exceptthe Pennsylvania district, and itisjessential' as is disturbed y the boiling of h m g that these oilsremain in a homogeneous erant beneath it and the escape of therefrigliquid state at all temperatures encountered erant thru it. When.boiling of the refrigin the refrigerating apparatus. By homoerantceases, the few bubbles formed by the geneous liquid state I mean thatthe oil must ebullition rapidly disappear. I'have also disremainsufficiently fluid to flow readily and covered that there are certainoils, not heremust rem in fr fromsuspen-ded solid bodies tofore used forrefrigerating apparatus, such as crystals or particles of paraflin atthe which when used in such an evaporator form temperatures encounteredin refrigerating a dee but light and fluify layer of sustalned practice,for example at temperatures as low bubb es. That is, the boiling of therefrigas 15 F. Attempts have previously been erant causes the oil tofoam and form alaymade to use paraflin base oils in refrigerating er ofbubbles which may even reach the top apparatus but it was found thatsolid paraffin of the evaporator. When boiling of the rewould separateout from such oils within the frigerant ceases, these bubbles do notimmeordinary temperature range of refrigerating diately disappearbut-retain their form for a t It a l f d th t t th a considerableperiod. The relative behav1or t ratures produced by ordinary refri 0fthe tWO oils mentioned above may be rougherat ng apparatus such oilswould congeal, 5 C p to boiling P Water and boll- Either the separationof paraffin or the coning soap solution respectively.

This discovery. has enabled me to devise a new method of lubricatingrefrigerating elation rendered the oil unfit for use in rerigeratingapparatus, and for these reasons paraflin base oils have not been used.

apparatus. accordance with this method I Ordinary paraflin oils have apour point use as lubricant in the apparatus one of the in theneighborhood of 30 F., whereas 1t has last-mentioned oils, which I termffoamang been usual, in ordinary domestic mechanical By t term I mean ny011 Whlch, refrigerating apparatus, to specify oil having when mixedwith refrigerant, is capable of pour. i t f -3() F, B thi i meantforming sustained bubbles or foam 1n appre-th t th 11 in Pour readily fa ciable quantities- In so doing I Prefer to tainer at this temperature.I have discovcalibrate the float 25 so ha h re ig ered that in the caseof foaming oils, oils of a level is CODSldGIabIy below the level 0f theconsiderably higher pour point may be used outlet, as indicatedin Fig-2- That I successfully. For example one of the foamleave an apprecmbleSpace between t S111" ing oils which I have used successfully has a faceof the q Whether 011 refmgemnt, pour point of 5 F. When this oil ismixed easily withdrawn without danger of splash ing liquid refrigerantinto the outlet. When the refrigerant is boiling, the oil (because ofits foaming characteristics) forms bubbles or bodies of. refrigerantvapor totally entwo liquid phases are formed which are generally calledthe sulphur dioxide phase and the oil phase. The sulphur dioxide phaseappears to be and acts very much like sulphur dioxide but is reall. asolutionof a small closed b films of 011. The suctlon roduced y J by thedbmpressor withdraws thesd bubbles Rroportlon of 011 m sulphur dloxldeg9 thru the exhaust tube and it will be 011 phase appears and acts verymuch hke Oll. evident that each time a bubble is drawn 0 i t th tl t, ti tit f ffi portlon of sulphur dioxide in 011. Inthe parerant vapor anda certain quantity of oil is tlcular case under dlscussion the 011 phasepositively returned to the compressor. Since r ma ns in a homogeneousliquid state and the oil foams up over the end of the exhaust has a pourpoint as low as -27 F. The reconduit, refrigerant vapor can not be with?duction of the pour point from ,5 to 27 "11 and the Outlet so that 011and Vapor may be with a refrigerant, such as sulphur dioxide,

but this is in fact a solution of a small pro-.

may possibly be due to the dissolving of the sulphur dioxide in the oil.

I hav found that a paraffin base oil made by the Kendall RefiningCompany, Bradford, Pennsylvania, and having the following physicalcharacteristics is suitable for my purpose:

Specific gravity at F .8665 Viscosity (Saybolt) at 100 F 94 secViscosity (Saybolt) at 21 F 973 sec. Flash point 360 F. Fire point 425F. Cold H SO absorption 2.48% Pour point 5 F.

While I have described my invention as ascribed to an evaporator of theflooded type it will be understood that the method of lubrication isequally applicable to other kinds of evaporators such as the dryexpansion type. Also while I have described my method of lubrication asinvolving a paratfin base oil, I wish it to be understood that theinvention is not limited to this type of oil, any oil having the abovedescribed foaming characteristics being. suitable. For example, I mayadd materials to asphalt base oils which will impart a foamingcharacteristic to such oils without detracting from their othercharacteristics which render them suitable for refrigeration.

What is claimed is as follows:

1. The method of operating refrigerating apparatus which consists incirculating through the apparatus a volatile refrigerant and oil capableof forming sustained bubbles in the presence of the refrigerant.

2. The method of removing both refrigerant and lubricant from arefrigerating evaporator which consists in evaporatin the liquidrefrigerant, forming sustained ubbles of refrigerant vapor and liquidlubricant, and removing the bubbles from the evaporator.

3. The method of circulating refrigerant and lubricant in arefrigerating system which comprises introducing liquid refrigerant andliquid lubricant into an evaporator, evaporating the refrigerant,forming sustained bubbles of refrigerant vapor and lubricant andremoving the bubbles from the evaporator.

4. The method of circulating refrigerant and lubricant in arefrigerating system which comprises introducin into an evaporatorliquid refrigerant an oil capable of formsustained bubbles in thepresence of the re r1 'gerant, evaporating the refrigerant,

forming sustained bubbles of refrigerant vapor and oil, and removing thebubbles from the evaporator.

5. Refrigerating apparatus comprising in combination a closed systemincluding an evaporating element and a condensing element connectedthereto, the system containing a volatile refrigerant and oil capable offorming sustained bubbles in the presence of the refrigerant.

6. The method of operating refrigerating.

apparatus which consists in circulating through the apparatus sulphurdioxide and oil capable of forming sustained bubbles in the presence ofthe refrigerant.

7. The method of removing sulphur dioxide and liquid lubricant from arefrigerating evaporator which consists in evaporating the sulphurdioxide, forming sustained bubbles of sulphur dioxide vapor and liquidlubricant, and removing the bubbles from the evaporator.

8. The method of circulating refrigerant and lubricant in arefrigerating system which comprises introducing liquid sulphur dioxideand liquid lubricant into an evaporator, evaporating the sulphurdioxide, forming sustained bubbles of sulphur dioxide and the lubricantand removing the bubbles from the evaporator.

9. The method of circulating refrigerant and lubricant in arefrigerating system which comprises introducing into an evaporatorsulphur dioxide and oil capable of forming sustained bubbles in thepresence of sulphur dioxide, evaporating the sulphur dioxide, formingsustained bubbles of sulphur dioxide vapor and the foaming oil, andremoving the bubbles from the evaporator.

10. Refrigerating apparatus comprising in combination a closed systemincluding an evaporating element and a condensing element connectedthereto and sulphur dioxide and oil capable of forming sustained bubblesin the presence of the refrigerant in the systerm.

In testimony whereof I hereto afiix my signature.

RALPH K. MILLER.

